Phytotoxicity of Y ₂ O ₃ nanoparticles and Y ³⁺ ions on rice seedlings under hydroponic culture

Due to the characteristics of both rare earth elements (REEs) and nanoparticles (NPs), Y₂O₃ NPs have been widely used in the fields of medicine, military industry, and agriculture, especially in the areas of electricity, light, magnetism, and catalysis. Given this widespread use, it is inevitable that Y₂O₃ NPs and soluble Y³⁺ will enter bodies of water through the processes involved in their preparation, application, and disposal. We sought to investigate the toxicities of Y₂O₃ NPs and Y³⁺ ions on rice seedlings (Oryza sativa L.), as well as the uptake and distribution of Y₂O₃ NPs under hydroponic conditions. Our results indicated that Y₂O₃ NPs and released Y³⁺ had no significant effect on the germination rate of rice. However, high concentrations of Y₂O₃ NPs (50 and 100 mg/L) delayed seed germination. As for rice root elongation, low concentrations (1, 5, and 10 mg/L) of Y₂O₃ NPs had a positive effect. Notably, when Y₂O₃ NPs concentration reached 20 mg/L and higher, root elongation was significantly inhibited. According to the physiological and biochemical characteristics of rice seedlings under Y stress, Y₂O₃ NPs ranging from 20 to 100 mg/L significantly reduced chlorophyll contents and root activity. Using ICP-MS and TEM analyses, Y₂O₃ NPs and Y³⁺ were shown to be mainly absorbed and accumulated in the roots. With Y₂O₃ NPs exposure, the Y transport coefficient from the roots to the shoots of rice was 1.94-7.55%. Comparatively, Y³⁺ ions had an insignificant effect on plant growth, with the phytotoxicity of Y being mainly produced by Y₂O₃ NPs.

Keywords: Phytotoxicity; Rice seedling; Uptake; Y(2)O(3) NPs; Y(3+) ion.